What is the minimum size for an unlisted driven grounding rod made of stainless steel?

The minimum size for an unlisted driven grounding rod made of stainless steel is indeed 1/2 inch in diameter and 8 feet long. This specification is outlined in the National Electrical Code (NEC), which sets standards for grounding electrodes to ensure safety and effective grounding for electrical systems.

The dimension of 1/2 inch in diameter provides a balance between sufficient surface area for conductive properties and structural integrity. The length of 8 feet ensures that the grounding rod can effectively penetrate the ground to reach a soil layer that provides a reliable grounding connection. This depth is critical in mitigating electrical hazards by allowing for adequate dissipation of any fault currents into the earth.

While the other options may differ in dimensions or materials, they do not meet the NEC standards for the minimum size or effectiveness of a grounding electrode intended for use in a safe electrical installation.